In technical optimization of existing systems, in order to improve the quality of user experiences and throughput of the systems, the high-speed uplink packet access technology is evolved continuously and at present a high order modulation mode of 16QAM has been introduced. The introduction of the high order modulation of 16QAM allows a user to transmit data at a higher rate. Accordingly, higher power is required to meet requirements of service quality, which causes a great change in the method of uplink power control as well as the method for a base station to determine a grant.
There are two methods for the base station to determine a grant: one is absolute grant and the other is relative grant. The grant method, whether absolute or relative, in fact is that the base station indicates an available power resource (which may corresponds to a grant value) to a user equipment based on various factors, such as allocable resources of the cell, channel quality indication of the user, size of the requested data etc., and notifies the user by an index or by way of relative rising/lowering, then the user equipment determines a rate at which data may be transmitted according to the power resource. It can be seen that the base station needs to know explicitly a corresponding relationship between the index and the grant value so as to ensure that the user equipment determines a rate at which data may be transmitted within an upper limit of power that the base station expects the user equipment to transmit.
After 16QAM is introduced, the previously defined corresponding relationships between indexes and grant values (powers) are no longer able to meet requirements. Thus, the 3rd Generation Partnership Project (3GPP) protocol introduces new tables of corresponding relationships between indexes and grant values for absolute grant and relative grant respectively, i.e., introduces higher grant values to meet the requirements for higher rate. At present, as specified in the protocol, there are two absolute grant mapping relationship tables usable by the E-AGCH channel. As illustrated in Table 1 and Table 2, a mapping table of absolute grant values, which is a table of relationships between absolute grant values and indexes before the introduction of 16QAM, is shown in Table 1, and a self-adapting mapping table of absolute grant values, which is a table of relationships between absolute grant values and indexes after the introduction of 16QAM, is shown in Table 2. Content of each of the tables contains two items: index numbers and absolute grant values.
TABLE 1Mapping table of absolute grant valuesAbsolute Grant ValueIndex(168/15)2 × 631(150/15)2 × 630(168/15)2 × 429(150/15)2 × 428(134/15)2 × 427(119/15)2 × 426(150/15)2 × 225 (95/15)2 × 424(168/15)223(150/15)222(134/15)221(119/15)220(106/15)219 (95/15)218 (84/15)217 (75/15)216 (67/15)215 (60/15)214 (53/15)213 (47/15)212 (42/15)211 (38/15)210 (34/15)29 (30/15)28 (27/15)27 (24/15)26 (19/15)25 (15/15)24 (11/15)23 (7/15)22ZERO_GRANT*1INACTIVE*0
TABLE 2Self-adapting mapping table of absolute grant valuesAbsolute Grant ValueIndex(377/15)2 × 431(237/15)2 × 630(168/15)2 × 629(150/15)2 × 628(168/15)2 × 427(150/15)2 × 426(134/15)2 × 425(119/15)2 × 424(150/15)2 × 223 (95/15)2 × 422(168/15)221(150/15)220(134/15)219(119/15)218(106/15)217 (95/15)216 (84/15)215 (75/15)214 (67/15)213 (60/15)212 (53/15)211 (47/15)210 (42/15)29 (38/15)28 (34/15)27 (30/15)26 (27/15)25 (24/15)24 (19/15)23 (15/15)22ZERO_GRANT*1INACTIVE*0
According to the current 3GPP protocol, the user equipment is notified via the air interface only of which absolute grant mapping relationship table to use, but the user equipment is not notified at the Node B application part (NBAP) interface, and there is no explicit specification either, such that the absolute grant values corresponding to the base station and the user equipment are obtained from different absolute grant value and index relationship tables, thereby resulting in inconsistency between allocation and use of the power resource by the base station and the user equipment, and eventually resulting in overload or reduced throughput of the system due to insufficient use of the usable power resource by the user equipment.